Two-piece joint-forming device for hardenable, area-covering structural material

ABSTRACT

An elongated device for forming surface joints in hardenable area-covering structural material such as freshly poured concrete comprising a bottom section and a top section that are temporarily coupled together when the device is forced into the initially soft material. The top section couples to the bottom section in such a manner as to transmit sufficient downward force on the bottom section to install it in the soft material. The bottom section has means for retaining itself within the material after it has cured or hardened so that the top section can be uncoupled and stripped from the bottom section.

United States Patent [1 1 3,838,930 Koch 1 1 Oct. 1, 1974 TWO-PIECEJOINT-FORMING DEVICE FOR 3,323,426 6/1967 HARDENABLE, AREA-COVERINGSTRUCTURAL MATERIAL 3:782:846 1/1974 Johnson 404/48 [76] Inventor:Vergil W. Koch, 105 Hobart Ave.,

San Mateo, Calif. 94402 [22] Filed: Nov. 8, 1972 [21] Appl. No.: 304,664

Related US. Application Data [63] Continuation-impart of Ser. No.202,261, Nov. 26,

1971, abandoned.

[52] U.S. Cl. 404/48 [51] Int. Cl. E0lc 11/02 [58] Field of Search404/48, 47, 65, 66, 68, 404/74, 72; 52/396; 49/475, 488, 498

[56] References Cited UNITED STATES PATENTS 1,730,067 10/1929 Fischer404/47 2,042,524 6/1936 Hall 404/48 2,540,251 2/1951 Fischer 404/472,949,828 8/1960 Cames 404/74 Primary Examiner-Nile C. Byers, Jr.Attorney, Agent, or FirmOwen, Wickersham & Erickson [5 7] ABSTRACT Anelongated device for forming surface joints in hardenable area-coveringstructural material such as freshly poured concrete comprising a bottomsection and a top section that are temporarily coupled together when thedevice is forced into the initially soft material. The top sectioncouples to the bottom section in such a manner as to transmit sufficientdownward force on the bottom section to install it in the soft material.The bottom section has means for retaining itself within the materialafter it has cured or hardened so that the top section can be uncoupledand stripped from the bottom section.

6 Claims, 4 Drawing Figures TWO-PIECE JOINT-FORMING DEVICE FORHARDENABLE, AREA-COVERING STRUCTURAL MATERIAL BACKGROUND OF THEINVENTION This application is a continuation-in-part application of Ser.No. 202,261, filed on Nov. 26, I971 now abandoned.

This invention relates to the formation of expansion joints in asettable, surface covering composition such as concrete as commonly usedin the construction airport runways and taxiways, roadways, buildingfloors and masonry or terrazzo decks such as plazas, walkways andpatios. More particularly, it relates to a twopiece joint forming devicethat can be inserted into a settable composition in its plastic stagesuch as freshly poured concrete, so that one piece can be removed toform the completed joint with a surface groove after the concrete hasset or cured.

Such joints in most settable compositions such as concrete are necessaryin order to prevent surface cracks due to expansion or contraction ofthe composition during curing and later on due to environmentaltemperature variations. In the prior art it has been known to use ajoint forming structure made of a plastic material formed as twoportions connected by a severable web. Such a structure, as shown in US.Pat. No. 3,330,187 was inserted in freshly poured concrete mix and whenthe concrete had hardened an upper portion was severed from the lowerportion buried in the concrete, thereby forming a surface groove.Although the aforesaid structure provided good results in manyinstallations, as when used between masonry or terrazzo tiles, it wasdifficult to use with efficiency in the con struction of large concreteslabs, such as roadways, aircraft runways and the like. The problemarose because this prior joint fonning structure was too flexible andwould bend or flex when forced vertically into freshly poured concrete.Thus, it became very difficult to maintain adequate straightness for thejoint grooves without the use of additional equipment, time and labor.Also, in the aforesaid joint structure the top portion once severed fromthe bottom portion became a waste product and was not reuseable. Thisnot only in creased its relative cost but also created a waste disposalproblem.

-A general object of the present invention is to provide an improvedjoint forming structure for settable compositions that overcomes theproblems and disadvantages of prior joint forming structures.

Another object of my invention is to provide a joint forming structurefor settable compositions comprised of two coupled but separable parts,one of which may be made of a harder and less flexible material than theother.

Another object of my invention is to provide a twopiece joint formingstructure for settable compositions comprised of mechanically coupledbut easily separable top and bottom parts wherein the top part couplesto the bottom part so as to enable a relatively large downward force tobe applied to it without any slippage and thereby enabling the structureto be buried rapidly and in a uniform manner in the composition.

Another object of my invention is to provide a joint forming structurefor settable compositions that is comprised of mechanically coupled buteasily separable top LII and bottom parts wherein the top part isreuseable after being removed from a bottom part buried in the cured orhardened composition.

Still another object of my invention is to provide a joint formingstructure for settable compositions which can be easily installed toform straightline joints with out the need for extra equipment orinstallation proce dures.

Yet another object of my invention is to provide a joint formingstructure for settable compositions which will form a clean, uniformgroove with predetermined dimensions in the surface of the hardenedcomposition when the upper part has been removed therefrom.

SUMMARY OF THE INVENTION The aforesaid objects are accomplished by anelongated joint-forming structure comprising a bottom section offlexible plastic material having a vertically elongated cross sectionwith horizontally extending serrations or tin-like portions on oppositesides and an upper coupling means. The latter, in one preferred form, isan integral bulbous portion that extends continuously along the top ofthe bottom section. A top section formed of a rigid plastic or metal hasa generally inverted U-shape in cross section with downwardly extendingleg portions that grip the bulb-like portion of the bottom section andtransmit uniform downward pressure to it when the elongated structure isforced vertically into the soft, settable composition such as freshlypoured concrete. When the composition has cured, the top section is heldat one end and pulled from the bottom section which remains lockedwithin the hardened composition by its side fins or serrations.

Other objects, advantages and features of the invention will becomeapparent from the following detailed description of one embodimentthereof which is presented with the accompanying drawings, in which:

FIG. I is a view in perspective showing a section of my two-piecejoint-forming device: as it appears when installed in a mass of concreteand before the top section has been removed;

FIG. 2 is a view in elevation and in section of my joint forming deviceshown just after it has been forced into freshly poured concrete withportions in phantom showing it before fully installed;

FIG. 3 is an exploded view in elevation and in section similar to FIG. 2showing the concrete in its hardened state with the top section of thedevice removed; and

FIG. 4 is a view in section showing another embodiment of my jointforming device with a modified form of fins on the lower section.

With reference to the drawings, FIG. 1 shows a jointforming structure 10embodying the principles of the present invention as it appears wheninstalled in a section of concrete such as may be used for a roadway,airport runway or other slab-type concrete structures. Generally, myjoint former may be: made in elongated sections of any convenient lengthhaving a constant cross section. Essentially, it is comprised of a lowersection 12 and an upper section 14 which are normally coupled togetherafter they are manufactured, but before the product is ready for use.The lower section as seen in cross section has a vertically elongatedmain body portion 16 with a width that preferably tapers downwardly arelatively small amount and has a curved or more abruptly tapered bottomedge 18. Vertically spaced apart and extending along both sides of thismain body portion are a series of fin-like portions 7 that taper from afairly thick root to a narrower outer edge. These fin-like portions tendto extend generally outwardly from the sides of the main body portiononly a short distance (e.g. one-sixteenth to one-eighth inch), but farenough so that even before the concrete has set or hardened, they actlike barbs or stops which prevent the lower member from floatingoutwardly. After hardening, these fins or fin-like portions 20 help tohold the joint former in place and they also coact with the concrete toreduce the leakage of water into the joint if the sealant should fail.Although the fins shown are fairly long and sharp in cross section,other forms of fin-like portions with a different or more blunt crosssection could be utilized within the scope of the invention. Forexample, as shown in FIG. 4, a series of horizontally extendingbead-like portions 20a are provided which accomplish the same retainingfunction as the portions 20.

Extending along the top of the lower section 12 is an integral bulbousprojection 22 having generally a circular shape which forms a pair ofsmall grooves 23 along its opposite sides. These latter grooves serve asa means for connecting the upper section 14 to the lower section 12 aswill be seen. The integral projection 22 must be sufficiently soft andcompressible so that it will compress to permit the removal of the uppersection 14 after the concrete or other composition has set or hardened.

The lower section 12 including the main body portion 16, the fins 20,and the top projection 22 is preferably formed as an integral extrusionor molded product from a plastic material such as plasticizedpolyvinylchloride (PVC), rubber, or neoprene. Plasticizedpolyvinylchloride having a specific gravity of around 1.3, and a Shore Ahardness of around 70 to 85, is a very suitable material since it can beformulated to be very durable. The specific gravity provides sufficientproduct weight to help prevent the joint former from floating out of thefreshly poured concrete. This material is firm enough to withstand theweight of the freshly poured concrete, and is sufficiently compressibleto respond to expansion of the hardened concrete without damage to theconcrete at the joint.

Now, the upper section 14 of my joint-former 10, as shown in the drawinghas generally an inverted U-shape with spaced apart downwardly extendingand convergent legs 24 that grip the projecting top portion 22 on thelower section 12. This upper member is preferably made from a relativelyhard and somewhat resilient plastic material such as rigid(unplasticized) polyvinylchloride (PVC). If desired, extruded aluminumor some other suitable metal can be used. Rigid PVC is a very suitablematerial since it is tough, smooth, and releases from the hardenedconcrete without the use of oils, greases, or other release agents whichwould later interfere with the adhesion of the caulking compound to thehardened concrete. The leg portions 24 curve outwardly at their upperends to form fillets 26 on opposite sides and are interconnected by aflat transverse portion 28. Extending downwardly from this transverseportion 28 these leg portions tend to converge toward each otheralthough their resiliency will allow them to be easily spread apart.Near the lower ends of the leg portions 24 are a pair of inwardlyextending ridge-like projections 30. These latter projections are shapedso as to fit snugly within the grooves 23 formed by the bulbousprojection 22. The upper surface of projections 30 is beveled or curvedto facilitate removal of the upper section 14 after the concrete hashardened. and the lower surface of the projections 30 is flat and restson shoulders 34 of the lower section 12 so as to transmit at least partof the force of insertion in the concrete to the lower section 12. Thelower ends of the legs 24 of the upper section 14 rest on a pair ofelongated shoulders 35 formed just below and on opposite sides of theprojection 22 of the lower section 12. These shoulders help to transmiteven more of the force of insertion into the concrete from the uppersection to the lower section. The aforesaid normal tendency of the legportions 24 to extend toward each other therefore causes the ridgelikeprojections 30 to actually grip the bulbous projection 22. The legs 24of the upper section, when assembled with the lower section, areslightly closer together at their lower extremities so as to form arecess 32 in the concrete which is slightly more narrow at the bottom,thereby providing a draft angle that facilitates the removal of theupper section 12 from the hardened concrete.

As shown in FIG. 2, when a section of my jointforrner 10 is to beinstalled the upper and lower sections are coupled together and avertical force is applied to press it into the freshly poured concreteor plastic composition. The upper section 14 is sufficiently strong andrigid so as to accept the downward force and transmit this force to thelower section.

FIG. 3 shows the joint-former 10 after it has been properly installedand the composition or concrete has cured and solidified. When thisoccurs, the upper cap section 14 is easily removed from the lowersection 12 to leave a clean, well-formed groove 32 above it. This grooveis now normally filled with a suitable sealant (not shown). The removedupper cap section is reuseable with another piece of lower section.

From the foregoing, it is seen that the present invention provides asubstantially improved joint-former over similar products of the priorart. The increased rigidity which can be provided by the upper capsection 14 makes it possible to install my joint-former along straightlines without using special equipment or expensive, time consumingprocedures. Yet, the lower section 12 can be more flexible and providethe compressibility required to accommodate expension factors. Whencoupled together the upper and lower sections are handled as a unitarystructure and yet the removal of the upper member from this structureafter its installation can be performed quickly without the need forspecial tools or labor. The groove 32 formed by the upper section isclean, straight and dimensionally precise and since it is reuseable, asubstantial saving in material is provided.

To those skilled in the art to which this invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the spirit and scope of the invention. The disclosures and thedescription herein are purely illustrative and are not intended to be inany sense limiting.

I claim:

1. A two-piece elongated joint-forming structure for use with settablecompositions used for slab-like installations comprising:

a lower section of relatively flexible material with a main body portionhaving a vertically elongated cross-section and a tapered or roundedlower edge, a plurality of spaced apart members projecting outwardlyfrom opposite sides of said body portion and a coupling member extendingalong the top edge of said body portion;

an upper section comprising a cap member of generally harder materialthan said lower section, having a transverse top portion that is widerthan the maximum cross-sectional width of said lower section andincluding leg portions extending downwardly from said top portion;

said leg portions and coupling member having interlocking means at fixedlocations thereon for releasably retaining them in assembled relation;

and means on said lower section forming elongated bearing surfaces forthe ends of said leg portions so as to transmit a driving force appliedto said cap section to said lower section.

2. The joint forming structure as described in claim 1 wherein saidcoupling means further comprises an elongated bulbous projection havinga substantially uniform cross-section and the interlocking meanscomprises a pair of grooves on one of said members and cooperatingdetent means on the other of said members.

3. The joint forming structure as described in claim 2 wherein saidbulbous projection has a generally circular cross-section.

4. The joint-forming structure as described in claim 1 wherein saidlower section is made from a rubber-like material having a Shore Ahardness of around to and said upper cap member is made from relativelyrigid material having a substantially greater hardness than said lowersection.

5. The joint-forming structure as described in claim 1 wherein saidcoupling member on the upper end of said body portion has a generallycircular cross-section forming grooves on its opposite sides and saidleg portions of said upper section includes elongated projections thatfit within said grooves.

6. The joint-forming structure as described in claim 1 wherein saidmeans forming bearing surfaces comprise a pair of elongated shouldersnear the upper end of said lower section that extend along oppositesides of and just below said coupling means, said leg portions of saidcap member having lower edges that engage said bearing surfaces tothereby transmit a driving force applied to said cap section to saidlower section.

1. A two-piece elongated joint-forming structure for use with settablecompositions used for slab-like installations comprising: a lowersection of relatively flexible material with a main body portion havinga vertically elongated cross-section and a tapered or rounded loweredge, a plurality of spaced apart members projecting outwardly fromopposite sides of said body portion and a coupling member extendingalong the top edge of said body portion; an upper section comprising acap member of generally harder material than said lower section, havinga transverse top portion that is wider than the maximum cross-sectionalwidth of said lower section and including leg portions extendingdownwardly from said top portion; said leg portions and coupling memberhaving interlocking means at fixed locations thereon for releasablyretaining them in assembled relation; and means on said lower sectionforming elongated bearing surfaces for the ends of said leg portions soas to transmit a driving force applied to said cap section to said lowersection.
 2. The joint forming structure as described in claim 1 whereinsaid coupling means further comprises an elongated bulbous projectionhaving a substantially uniform cross-section and the interlocking meanscomprises a pair of grooves on one of said members and cooperatingdetent means on the other of said members.
 3. The joint formingstructure as described in claim 2 wherein said bulbous projection has agenerally circular cross-section.
 4. The joint-forming structure asdescribed in claim 1 wherein said lower section is made from arubber-like material having a Shore A hardness of around 70 to 85 andsaid upper cap member is made from relatively rigid material having asubstantially greater hardness than said lower section.
 5. Thejoint-forming structure as described in claim 1 wherein said couplingmember on the upper end of said body portion has a generally circularcross-section forming grooves on its opposite sides and said legportions of said upper section includes elongated projections that fitwithin said grooves.
 6. The joint-forming structure as described inclaim 1 wherein said means forming bearing surfaces comprise a pair ofelongated shoulders near the upper end of said lower section that extendalong opposite sides of and just below said coupling means, said legportions of said cap member having lower edges that engage said bearingsurfaces to thereby transmit a driving force applied to said cap sectionto said lower section.